If the tool is invoked without the --commit switch, /etc/machine-id is initialized with a valid, new machined ID if it is missing or empty. The new machine ID will be acquired in the following fashion:

1. If a valid D-Bus machine ID is already configured for the system, the D-Bus machine ID is copied and used to initialize the machine ID in /etc/machine-id.

2. If run inside a KVM virtual machine and a UUID is was configured (via the -uuid option), this UUID is used to initialize the machine ID. The caller must ensure that the UUID passed is sufficiently unique and is different for every booted instance of the VM.

3. Similarly, if run inside a Linux container environment and a UUID is configured for the container, this is used to initialize the machine ID. For details, see the documentation of the m[blue]Container Interfacem[]

[1]

.

4. Otherwise, a new ID is randomly generated.

The --commit switch may be used to commit a transient machined ID to disk, making it persistent. For details, see below.

Use systemd-firstboot(1) to initialize the machine ID on mounted (but not booted) system images.

OPTIONS

The following options are understood:

--root=root

Takes a directory path as argument. All paths operated will be prefixed with the given alternate root path, including the path for /etc/machine-id itself.

--commit

Commit a transient machine ID to disk. This command may be used to convert a transient machine ID into a persistent one. A transient machine ID file is one that was bind mounted from a memory file system (usually "tmpfs") to /etc/machine-id during the early phase of the boot process. This may happen because /etc is initially read-only and was missing a valid machine ID file at that point.

This command will execute no operation if /etc/machine-id is not mounted from a memory file system, or if /etc is read-only. The command will write the current transient machine ID to disk and unmount the /etc/machine-id mount point in a race-free manner to ensure that this file is always valid and accessible for other processes.

This command is primarily used by the systemd-machine-id-commit.service(8) early boot service.

-h, --help

Print a short help text and exit.

--version

Print a short version string and exit.

EXIT STATUS

On success, 0 is returned, a non-zero failure code otherwise.

SEE ALSO

systemd(1), machine-id(5), systemd-machine-id-commit.service(8), dbus-uuidgen(1), systemd-firstboot(1)

NOTES

1.

Container Interface

www.freedesktop.org/wiki/Software/systemd/ContainerInterface